Guys,
I'm really stacked...Please read this thread http://diyaudio.com/forums/showthread.php?s=&threadid=25862
and give me any clue about what is happening. Nobody faced this kind of problem?
I'm really stacked...Please read this thread http://diyaudio.com/forums/showthread.php?s=&threadid=25862
and give me any clue about what is happening. Nobody faced this kind of problem?
I think a measurement of the impedance down below 200 Hz might be an appropriate step. It will let you really see what's going on with the box tuning. If you could post that, along with the raw driver's measured impedance curve, that might be useful.
I don't usually make language notes, but "I'm really stacked" has an unfortunate implication in English (at least in American English). Well, fortunate if you're a girl, unfortunate if you're not.
I don't usually make language notes, but "I'm really stacked" has an unfortunate implication in English (at least in American English). Well, fortunate if you're a girl, unfortunate if you're not.
So,
If I understand right, you tell me to measure the impedance driver mounted in the enclosure?
I have the impedance driver measured in free air, so I will post both of them today.
Sorry about my language, I'm doing my best.
If I understand right, you tell me to measure the impedance driver mounted in the enclosure?
I have the impedance driver measured in free air, so I will post both of them today.
Sorry about my language, I'm doing my best.
You do great in English- it's just that you've run into slang and idiom that I'm sure they don't teach in school!
Yes, you should absolutely look at impedance in the box. That will definitively tell you if your tuning is correct or not.
Yes, you should absolutely look at impedance in the box. That will definitively tell you if your tuning is correct or not.
Ok,
I will do this mesurement in a few hours and I will post it.
But I'm sure that the impdance curve will not look like the one in MathCAD sheets...
I will do this mesurement in a few hours and I will post it.
But I'm sure that the impdance curve will not look like the one in MathCAD sheets...
Somebody wrote in my last thread that I should check the Cone excursion...but I didn't really understood what he want to say with this. What do you think?
Well, first things first. Let's see if you've hit the target at the small-signal level.
What sort of volume (sound level) were you using for the frequency response measurements?
What sort of volume (sound level) were you using for the frequency response measurements?
One thing to be careful of is that you're actually measuring small-signal parameters. Keep the volume down.
Yes,
At every mesurement aI check the VU meter from Speaker Workshop, to be around 25.000.
The volume is indeed down
At every mesurement aI check the VU meter from Speaker Workshop, to be around 25.000.
The volume is indeed down
Well, I mean not just the input level for Speaker Workshop, but the actual volume that the speaker is running, i.e., loudness. Thiel-Small assumes that the volumes are relatively low.
The speaker is conected directly to the line out of the sound card, I think it's about 0.1 W there...
Here are the Thiele-Small and box parameters you posted in the other thread:
Qts=0.570
Qms=2.490
Qes=0.740
Vas=4,44 l
Fs=82 Hz
Re=3.690
BL=3.67000 N/A
Sd=65 cm^2
Enclosure volume=27 l
Vent diameter=5 cm
Vent length=7 cm
The box volume is six times the Vas!
In a closed box, putting a speaker in an enclosure six times the Vas is a true Infinite Baffle-that is, the enclosure has no effect on the speaker. It is the same as mounting the speaker on a single board of infinite width and height.
A reflex six time the Vas? The only thing I can say is I called Pyle tech help years ago and asked about a speaker of Qts=0.55 in a box about twice the Vas. "Once you get much over the Vas, the air in the enclosure doesn't have much effect anymore on the speaker," the tech said.
Be that as it may, I do believe the problem is that the box is six times the Vas of the speaker, the speaker and box air have very little relationship, and so the speaker thinks it is vibrating into free air.
Regardless of what the simulations say, that is why you are getting weak port output that is very near the listed Fs of the driver-it is operating in a free air situation.
I believe these programs have relevance when the Vas and box volume have a closer relationship-even a box twice the Vas is okay. But six times the Vas? I tend to doubt it.
Anyway, that is my guess. The speaker thinks it is operating in a free air situation, and is acting like it.
Qts=0.570
Qms=2.490
Qes=0.740
Vas=4,44 l
Fs=82 Hz
Re=3.690
BL=3.67000 N/A
Sd=65 cm^2
Enclosure volume=27 l
Vent diameter=5 cm
Vent length=7 cm
The box volume is six times the Vas!
In a closed box, putting a speaker in an enclosure six times the Vas is a true Infinite Baffle-that is, the enclosure has no effect on the speaker. It is the same as mounting the speaker on a single board of infinite width and height.
A reflex six time the Vas? The only thing I can say is I called Pyle tech help years ago and asked about a speaker of Qts=0.55 in a box about twice the Vas. "Once you get much over the Vas, the air in the enclosure doesn't have much effect anymore on the speaker," the tech said.
Be that as it may, I do believe the problem is that the box is six times the Vas of the speaker, the speaker and box air have very little relationship, and so the speaker thinks it is vibrating into free air.
Regardless of what the simulations say, that is why you are getting weak port output that is very near the listed Fs of the driver-it is operating in a free air situation.
I believe these programs have relevance when the Vas and box volume have a closer relationship-even a box twice the Vas is okay. But six times the Vas? I tend to doubt it.
Anyway, that is my guess. The speaker thinks it is operating in a free air situation, and is acting like it.
> The speaker is conected directly to the line out of the sound card, I think it's about 0.1 W there...
Are you sure? Does your sound card have a (good enough) power amplifier built in?
Well, if not, it's likely that we have found the source of your odd measurements...
Hope this helps.
Are you sure? Does your sound card have a (good enough) power amplifier built in?
Well, if not, it's likely that we have found the source of your odd measurements...
Hope this helps.
<Are you sure? Does your sound card have a (good enough) power amplifier built in?
Well, I think any sound card have enough power for nearfield mesurements. In nearfield, the mic is very close to the driver (1,5 mm).
If I want to take farfield measurements, of course, I need an amplifier...
For kelticwizard...
I think this is a very good question.... In a way I feel it but nobody put this problem in this forum, maybe it's very obvious...
You gave me something to think...I'm waiting other guy’s opinion...but I'm 90% that you are right. Thank you very much kelticwizard !
Well, I think any sound card have enough power for nearfield mesurements. In nearfield, the mic is very close to the driver (1,5 mm).
If I want to take farfield measurements, of course, I need an amplifier...
For kelticwizard...
I think this is a very good question.... In a way I feel it but nobody put this problem in this forum, maybe it's very obvious...
You gave me something to think...I'm waiting other guy’s opinion...but I'm 90% that you are right. Thank you very much kelticwizard !
That sounds odd to me, as it is not really a quastion of 'power', but of the sound card's output impedance. If your card is not designed to drive low impedance loads (I assume you use a 'regular' speaker) then you shouldn't expect predictable behavior.
I'd suggest you to connect a power amplifier between sound card output and speaker input. The intention is not to increase the delivered 'power', but to rule out any inability of the sound card to drive high loads (thus turn the volume down 😉 ).
Sek,
I'm using a circuit made special for this, like Speaker Workshop indicates. Are you familiar with Speaker Workshop?
I'm using this software to measure also T/S parameters, and it's working fine, so I don't think is a problem with the volume levels.
On the other hand, I post below my impedance results with the driver mounted in the enclosure, one with the vented port covered, one with the port leaved open. It’s pretty clear that the port almost doesn’t have any influence...I THINK THE BOX IS JUST TOO BIG FOR THIS DRIVER...But I want some confirmations about that, and what is the relation between VAS and the Volume of the enclosure. I think is very important, and nobody seems to talk about this.
I'm using a circuit made special for this, like Speaker Workshop indicates. Are you familiar with Speaker Workshop?
I'm using this software to measure also T/S parameters, and it's working fine, so I don't think is a problem with the volume levels.
On the other hand, I post below my impedance results with the driver mounted in the enclosure, one with the vented port covered, one with the port leaved open. It’s pretty clear that the port almost doesn’t have any influence...I THINK THE BOX IS JUST TOO BIG FOR THIS DRIVER...But I want some confirmations about that, and what is the relation between VAS and the Volume of the enclosure. I think is very important, and nobody seems to talk about this.
FWIW, I think KW is dead right. An impedance curve will confirm this. I should have paid more attention to the spec'd Qts- a value that high almost always means a driver meant for sealed box or open baffle use.
I don't think the Qts is relevant. The main idea is that the Volume of the box is just too big. Even if the Qts was 0,3, I think the results where the same.
But now I have a bigger question: How big can be the volume of the box for a given Vas of the driver? Nobody seems to treat this subject on the forum. Does it matters if the box is sealed or bass-reflex?
But now I have a bigger question: How big can be the volume of the box for a given Vas of the driver? Nobody seems to treat this subject on the forum. Does it matters if the box is sealed or bass-reflex?
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